The debate around the Facebook group Women Who Eat on Tubes has thrown up a number of interesting questions when it comes to privacy.

On Friday, its founder claimed Facebook deleted the group, but the social network said it was deleted by accident. The group has since been reinstated and turned into a private group by one of its administrators.

Tony Burke, the group's founder, has defended the group as "art" and "observational study" while its critics have called it sexist and inappropriate. The group itself is not unique – there are a slew of Facebook groups, Tumblrs and Subreddits which feature photographs of people taken without their knowledge.

Where do you draw the line when it comes to taking photos in public? Is everything fair game if you're doing it in public? Or should social media sites be cracking down on people who post pictures without people's knowledge?